It is well known to provide impact absorbing systems, often called “crash cushions” or “crash attenuators”, adjacent to rigid structures such as pillars, bridge abutments, lighting poles and the like for the purpose of absorbing vehicle impact energy and minimizing the effects of impact on the vehicle, the vehicle occupants and the structure being protected.
There are many forms and types of energy absorption barriers.
U.S. Pat. No. 5,851,005, issued Dec. 22, 1998, discloses an energy absorption barrier assembly including multiple pairs of ground engaging support uprights interconnected to one another by overlapping side panels. The side panels and uprights are connected together by inter-engaging slides so that an impact at the end of the barrier assembly can cause relative movement between the uprights, between the side panels, and between the uprights and the side panels. Located between the uprights and secured thereto are a plurality of energy absorbing metal plates configured in such a way that they collapse in a controlled manner upon vehicle impact to absorb impact forces.
U.S. Pat. No. 6,811,144, issued Nov. 2, 2004, discloses apparatus for absorbing energy when impacted by a vehicle that includes relatively movable vertical, spaced supports supporting modules extending between the supports. The modules are collapsing containers defining a pressurizable interior. The modules include two module segments, the side wall of the module forming a truncated cone at each of the module segments.
Cables extend between front and rear anchor structures of the apparatus and pass through cable passageways in the supports sized to allow relative slidable rotation between the cables and the guide members upon application of suitable forces caused by head on vehicle impact.
The supports are in the form of steel support frames extending upwardly from the ground.
It is also known to utilize elongated members such as metal tubes positioned between relatively movable supports which collapse when endwise forces are applied to the apparatus upon vehicle impact. Typically, however, in such arrangements the positioning of the tubes and the movable supports engaging the tube ends are stabilized in only one plane. Eccentric loading thus becomes a problem and the tubes between adjacent supports are not subjected to even compression by the relatively movable supports. This results in uneven collapse of the tubes, causing stability and crash control problems, even failure of the system.